A "random genetic error" (by definition) is not an argument for sex being a spectrum.

>A genetic condition in which a male is born with an extra copy of the X chromosome

So still a male, got it.

It sure is an argument for sex being a spectrum.

The word "error" is a social construct. I prefer "variation", which also is a social construct, but doesn't imply a judgment. (Of course, judgments are social constructs.)

"Whoa look, a manufacturing error caused this quarter to have an extra edge"

shocked realization

"Of course! Number of sides of a coin is a spectrum!"

Generally a quarter with a manufacturing error that big is trashed. It is also ok to use the word "error" for quarters. Things are not people.

In any case the number of sides of a coin is not a binary. It's just 2.

It seems cruel to use a metaphor of "manufacturing error" to describe intersex people. While I think "sex is a spectrum" is perhaps not how I would phrase it because it lets people muddy these kinds of arguments together, I think it's pretty well-accepted that there are people who are neither fully male nor female, i.e. intersex. "Manufacturing error" is a human classification: after all, nature makes no judgments on what is "correct" and what is not.

Just like "gender is a spectrum", "sex is a spectrum" is a simplified map of a complex territory.

> simplified map of a complex territory

Bingo. This is what scientific terminology aspires to. Except “sex is pretty darn binary” is a useful, meaningful simplification, while “sex is a spectrum” is at best a fundamental misunderstanding of what a spectrum is, and at worst a politically motivated conflation of intersex conditions with gender variation.

Eh, I think you can get various axes on a biological sex spectrum even if you consider the the definition of biological sex: if someone has male gonads and XY chromosomes but has undergone sex reassignment surgery and is undergoing estrogen hormone replacement theory, would you still classify them strictly biologically male if they don't meet two of the four generally used criteria for sex? And in the case you don't believe that all those criteria should be used for determining biological sex, then that's another thing people need to agree on. I think characterizing biological sex as a spectrum can be a useful way of thinking it, but I think people end up dragging the culture war debate into it.

> if someone has male gonads and XY chromosomes but has undergone sex reassignment surgery and is undergoing estrogen hormone replacement theory, would you still classify them strictly biologically male if they don't meet two of the four generally used criteria for sex?

Yes, because sex is a description of an observed natural phenomenon, not a taxonomy of medical interventions.

Not everyone agrees with that interpretation of sex, though, and reasonable people can choose to interpret sex as a collection of biological traits, medical interventions or not.

If a computer system produced the values 0 or 1 most of the time, and 2 a small percentage of the time, we wouldn't call it "pretty darn binary".

Plenty of intersex people are gender variant as well. See for example Dana Zzyym, who is intersex and uses they/them pronouns. They fought for nonbinary gender markers in passports.